Past perfect tense needs to be handled with care. It is most useful in the narrative genre and is seldom needed in Task 2 writing. However, Task 1 essays occasionally present an opportunity to use past perfect.

Sample text

In general, Facebook had by far the highest number of active users per month, and this number increased by more than 50% during the period. Despite having far fewer users per month, Twitter experienced a similar increase in numbers, but was overtaken half way through the period by Instagram.

In detail, Facebook already had a billion active users in 2012, but by 2015 this figure had increased to more than 1.5 billion. Twitter was in second place until 2014 when the monthly number of active Instagram users began to exceed that of Twitter users, and by 2015 Instagram had taken a 0.1 billion user lead over Twitter, forcing Twitter into third position. Similarly, by 2015 Snapchat had attracted only half as many active users per month as Instagram.

Analysis

Notice the structural use of past perfect in the detail section. I admit that I went a bit mad with it, but I strongly recommend this structure:

By + past time expression + subject + V3

Final task

Take another look at your own text. Did you use my past perfectstructure? If not, can you edit your text so as to include it in at least one sentence? Please share your writing in the comments section!